This invention relates to a method of producing electronic devices having electrodes formed on the surface of a ceramic body and in particular to a method of producing such electronic devices including the step of correcting the resistance values of the produced electronic device.
FIG. 5 shows a thermistor element 11 as an example of prior art electronic device, having electrodes 13 and 14 formed on the two main surfaces of a thermistor body 12 comprising a ceramic material with negative temperature characteristic comprising several kinds of transition metal oxides. To produce such thermistor elements, a mother thermistor wafer is prepared first and cut into many parts. In other words, a mother wafer with a relatively large surface area is prepared first, electrodes are formed all over its main surface, and this mother thermistor wafer is cut, say, by a dicing process, according to the specified size of the thermistor elements 11.
Like other kinds of resistor elements, however, thermistor elements must have their resistance values within a specified target range according to a product standard. On the other hand, the resistance values of produced thermistor elements usually vary because of the non-uniformity not only in the resistance value of the thermistor body material but also in the size of the diced elements. Thus, there have been efforts both to reduce the variations in the material and to improve accuracy in dicing.
In spite of all such efforts, however, it is difficult to make the variations in the resistance value of produced thermistor elements extremely small. In fact, there were always not a few with resistance values outside the allowable range mixed among produced thermistor elements. In other words, the fraction of acceptable products was not sufficiently high and the efforts to reduce the production cost of thermistor elements have not been successful.